Radio signaling system



INVENTOR ATTORNEY Nov. 27, 1923. I 1,475,219

R. BOWN RADIO SIGNALING: sYsTM Fi1e d Nov. 1, 1920 2 Sheets-Sheet 2 INVENTOR av/wa ATTORNEY Patented Nov. 27, 1923.

hihihihi@ STARS PATENT QFElCE.

RALPH BOWN, F EAST ORANGE, NEW JERSEY, ASSIGNOE TO AMERICAN TELEPHONE AND TELEGRAPl- COMPANY, A CGBPORATON 0F NEW YORK.

RADIO SIGNALNG SYSTEJJ'..

Application led November l, 1320. Serial No. 421,086.

To all whom t may concern:

Be it known that l, Rama-r BowN, residing at East Grange, in the county or" Essex and State oit New Jersey, haveinvented certain improvements in Radio Signaling Systems, which the following is a speciication.

This invention relates to radio signaling systems and especially to an arrangementwhereby the wave lengths of the various transmitting channels in a multiplex radio system may be controlled and interference 'thereby prevented.

ln multiplex .radio systems which are characterized by the operation ot' a plurality ot transmission channels under centralized control there arises the possibility of interit'erence between the secondary stations, which arey designed to operate with kthe various channels ot the central station, unless special means are provided to avoid such interference.

rlhis invent-ion providesa method of operation which furnishes a positive way for securing the proper selection et frequencies tor the transmission channels between the transmitting and the receiving stations in a coordinated radio system. Although this "ention is applicable to any system of radio transmission, it is especially designed to 'facilitate the operation ot a central multiradio station having a plurality ot channels over which transmission may bc maintained with a corresponding number ot secondary radio stations. rlhe arrangement disclosed herein lends itsellz particularly well to the maintenance of radio telephonie communir-ationA between a multiples: shore station and a plurality ot ship stations in u. manner which will be more clearly described hereinafter. r

This invention will be better understood un the following description when read in inection with the attached drawing, o' which Figure l represents diagrammatically the circuit arrangements of a system comprising a central multiplex station and a secondary station; Fig. 2 represents the circuit arrangement ot a system comprisir two secondary stations which are designed Vfor intercommunication there-between; and Figs. 3 and 4 represent frequency scales intended to show an arrangement of the fre- ;uencies at the central the secondary stations whereby interference between channels is avoided.

=n rig. l, A. represents a primary station a secondary station which may be one plurality ot similar stations adapted to i .intain transmission with station A.' At station A, a source ot high frequency continuous oscillations 1 which may be ot any well-known type, such as the well-known vacuum tuoe oscillator is connected with a modulator 2, with which is also connected a source ot low frequency signals 3'. llhe output side ot the modulator is, in turn, connected with the amplifier 1, the output side oi which is coupled Tith an antenna 5. The receiving circuit at the central station A comprises a balanced loop receiver 6, which is so designed that it will not be affected by oscillations of the frequency transmitted from the antenna 5 ot the transmittingcircuit at station A. The balanced receiver will, however, respond to oscillations ot a predetermined frequency and will impress them upon a demodulator 7, with which is connected a local source ot demodulating` current S, The local source ot oscillations 8 is intended to impress upon the dernodulator oscillationsot such frequency that, when beat with the oscillations ot the received trequen-cy, the resultant oscillations will lie within such a' range ot lrequency as to pass through the band filter 9 and be impressed upon the detector 10. The signa-l wave which is superimposed upon the received oscillations will be detected thereby.

rlie secondary station B comprises a is liitting and a receiving` circuit, each having its respective antenna but it is to be understood that the transmitting and receiving circuits may be so related as to operate in connection with a single antenna. ln the arrangement disclosed, 11 represents source ot high frequency oscillations, aving' associated therewith controlling means 12 for varyingthe frequency ot the oscillation circuit. rlhe output side ott the oscillator is connected with a modulator 13., with which also is connected a. source oil low frequency signaling current 14. The modulated high trequency oscillations are amplified by an amplierV 15 and then impressed upon the transmitting antenna` 16. |The receiving circuit comprises a receiving antenna 17, which is responsive to reception frequency and which is adapted to impress the received oscillations upon a demodulator The antenna 17 is also responsive to oscillations transmitted by the antenna 16 oi the transmittting circuit at station B. The oscillations of the frequency or 600,500 cycles (assuming that the device 21 produces oscillations of 500 cycles) received from the antenna 5 of the primary station, together with oscillations of the frequency of 57 0,000 cycles transmitted by the antenna 16, are beat together by the demodulator 18 and the resulting oscillations ot 30,500 cycles, which is the proper range ot trequency to pass through the band filter 19, will be impressed upon the detector 20. The resultant low frequency signal wave ot 500 cycles will be perceived thereby.

Fig. 2 shows the relation existing when two similar secondary stations are transmitting between themselves. ln this ligure, parts which are similar to those shown in Fig. 1 have been given the same designating numerals. The stations represented by C and D may, for example, represent two ship stations which are attempting to establish communication between themselves. ln this arrangement, the antenna 6 is not balanced against the transinittingl antenna 5, and con sequently it will respond to oscillations transmitted from the latter antenna, as well as from the oscillations from antenna 16 connected with the transmitting circuit ot station D. And in a. similar manner, the receiving antenna 17, associated with station D, will resepond not only to oscillations transmitted by antenna 5, but also to oscillations transmitted by antenna 16.

No claim of inventorship is made by the applicant upon the circuit arrangements herein disclosed. These arrangements are substantially the same as those disclosed in the copending application oi" Farrington, Series No; 326,986, dated September 27, 1919. In the Farrington application there is disclosed and claimed means for utilizing a fractional part of the unmcdulated carrier wave, which is transmitted from a secondary station to beat with the modu lated frequency received at the saine secondary station 'from the rcn'iote transmitting station and to obtain thereby a beatY frequency, by means of which a signal from the remote station may be detected. It is the object ot the applicant-s invention to utilize the means disclosed in the Farrington application in carrying out a method whereby the Ytreqruency of transmission Ytrom secondarl, stations to a multiplex cent-ral station or between two secondary stations in communication with each other may be so controlled that interference between two or more secondary stations may be prevented.

Considering the arrangement shown in Fig. let it be assumed that the station B desires to communicate with station A. The secondary station B would call station A, using therefor a standard-calling wave length and would be advised by station A as to the proper channel over which comv munication should be established. liet it be assumed that station et has three channels ol" conununication represented, tor example, by the .frequencies ot 600,000, 540,000 and i150,000 cycles respectively as shown in Figs. 3 and As soon as 'the station has advised the ailing secondary station as to the proper channel of communication, it would begin to transmit oscillations ot the ire qucncy represented by the designated channel.. The transmitted oscillations might either be modulated or uninodulated pro vided suitable signal indicating ineens associated at the receiving end oif the systen'i, since the invention is not limiting to special type ot radiated signal. Modulated oscillations may be produced by operating the tuning forli 21 in 'liront of the 'transmitter 3, associated with the low frequency naling circuit and for the purpose of describing the invention, a system involving the use of modulated oscillations will be as sumcd. These modulated high frequency oscillations would be received by the receiving antenna 1T ot station ll. The antenna 1i' will also receive oscillations which are genen ated by the oscillator 11, associated with the local transmitting circuit. The oscillations of the two frequencies are together passed into the demodulator 18, which produces the diil'ercnce v'frequency of the two waves impressed upon the demodulator. ln order that the resultant wave might be detected, the oscillations oii'the difference frequency must pass through the band filter or selective circuit 19. Thus, the ditlerence in frequency between the standard transmitting wave the primary station A and the transmitting wave ot the secondary station must lie within a certain range, in order that oscillations, whose frequency equals the di iiiference between the frequencies of the two transmitting waves, may. pass through the band lilter and be detected by a suitable deiecting device. It will t "it the transmitting frequency ot' each channel of a primary station is iixed in accordance with a definite wave length schedule -such as is shown in Figs. 3 and 4l, and, likewise, the channels of the adjacent primary stations are/'similarly fixed, any secondary station must seelr the proper assigned frequency ior any L articular channel ot transmission, in order to establish communication over the channel assigned by thc primary station with which it desires to communicate. is to say, in order tor station B to communicate with station A, the frequency ci" the oscillations radiated by the antenna 16 must be suoli that, when beat with the oscillations radiated from antenna 5, will produce a band ot oscillations adapted to pass through the band filter 19. In other words, the band That' filter i9, coupled With the controlled frequency transmitted from the primary station A over antenna 5, constitute means for controlling the frequency that the secondary station B must maintain, in order to communicate With the primary station fr. it will be seen, therefore, that this method or system enables the primary stations to control the radiating frequency of the secondary stations and thereby prevents interference between the said secondary stations, Which would result if such secondary stations were not given positive means to determine When their transmitting frequency Was of the proper magnitude for maintaining transmission, Without interfering With the transmission from neighboring secondary stations. For example, if the primary station A has assigned to the secondary station the use of channel No. l, which, as Will be seen by the scale of Fig. 3, has a frequency of 600,000 cycles, the operator at the secondary station Will begin to raise (or lower) the frequency of his oscillator ll until it approaches the desired magnitude, Which is manifested by the detection of the signal in the output circuit of detector 20. The operator can, with a little practice, vary his transmitting frequency up and down the scale, so that the signal incoming from antenna 5 disappears by running alternately out one side and then the other, of the range of the band of the selective circuit 19 and he can adjust the difference frequency to the centre of this band and thereby insure that speech or other multi-frequency signals, Which latter may be used in modulating the oscillations transmitted from the primary station A, Will fall Within the range of the selective circuit 19 and Will not be distorted.

The method of controlling transmitting wave lengths in a multiplex radio system will be apparent from the diagrams shown in Figs. 3 and 4. Thus, Fig. 3 shows a desirable arrangement for the distribution of the channels associated With three primary stations A, A, and A, and nine secondary or ship sta ions and the frequencies of the channels. Stations A, A., and A, cach hayv three channels, which are assumed to be suliicientljf Widely separated geographically and the frequencies sufficiently Widely separated electrically, as to be non-interfering among themselves. The channels of station A are numbered arbitrarily l, l and 7. those of station 13s 2, 5 and F. and those of station A2, 8, 6 and 9. The frequency of each channel may be determined by the scale at the left-hand side of 'the diagram. The ship stations have been given corresponding numbers priiied. It ll be seen from this diagram that if ship :tation l is operating over channel l with Nation A, and ship station Ai is operating crei' channel l With the same station, there exists sufficiently Wide separation between the frequencies of the tivo operating channels as to prevent interference there-between and, similarly, the ship stations are separated by frequency space of at least 10,000 cycles from the frequency range of the nearest channel transmitted from more remote primary stations than that with which the ship station may be operating, so that there is slight possibility of interference from this source. lt' Will be seen, therefore, that by means of an arrangement such as has been disclosed herein, interference between the transmitting frequencies of ,neighboring stations in a multiplex system is substantially eliminated because, as soon as the operator secondary sta-tion brings his frequency up to the desired transmitting frequency, he Will begin to receive oscillations through the band filter of his receiving circuit and thereby be apprised of the'fact that his transmitting frequency is approaching its proper Value. ln other words, this system provides a definite transmitting frequency for cach ship channel and means to indicate when such frequency is being transmitted.

lt will be noted. that, in describing the operation of the system in which this invention is embodied, reference has been made to the operation of a certain secondary station with a channel of a specific primary station. It is to be understood that any secondary station is capable of operating over a Wide range of Wave lengths, and consequently is adapted to maintain transmission over any channel of any primary station, selectii'ig assigned channel on the manner heretofore described.

The arrangement disclosed in Fig. 2 is, as stated, substantially the same as that shown in Fig. l, station C corresponding to primary station A and station D to station B. ln order to effect the proper ope-ration of this arrangement, the oscillation frequency of the transmitting circuit of station C is held constant and the operator at secondary station l) Will operate to obtain the proper` beat frequency in a similar manner as described in connection F ig. l.

lt is to be understood that, although this method has been described in connection with certain specific circuit arrangements, it is capable of being' used in other and different arrangements, Without departing from the spirit and scope of the appended claims.

lfilhat is claimed is:

l. ln a multiplex radio system comprising primary and secondary stations, the method of controlling the transmitting frequency of a secondary station, which consists in transmitting from the primary station a modulated Wave of fixed frequency, beating the received modulated Wave at the said secondary station With the unmodulated trans- CII -"itted Wave of the said secondary station aud adjusting the frequency of the said unmodulated transmitted Wave until the difference in frequency between the received modulated wave and the unmodulated transmitted wave Will be of such magnitude as to pass through a selective circuit associated with the receiving circuit of the said secondary station.

Qi. ln a multiplex radio system comprising primary and secondary stations, the method of controlling the transmitting frequency of cach secondary station, which consists in transmitting from the primary station a modulated Wave of fixed frequency, receiv ing the said modulated Wave at the secondary station, generating at the secondary station an unmodulated transmitting Wave' and impressing a portion of the unmodu" lated Wave upon the secondary receiving circuit, together with the modulated received wave, varying the frequency of the unmodulated Wave until the beat frequency of the two Waves lies within the frequency range of a selective circuit and impressing the said beat frequency upon detecting apparatus.

3. In a multiplex radio system comprising,

a plurality of primary and a plurality of secondary stations, each of the said primary stations having a plurality of transmitting channels, a method of controlling the transmitting frequency of cach secondary station, which consists in transmittingl over each ahannel of each primary station a modulated Wave of fixed frequency, which differs from that of the neighboring channels by a definitely fixed amount, assigning each of said secondary stations to its respective channel, generating an unmodulated transmitting Wave at each secondary station and beating the said unmodulated wave With the modulated Wave of the proper channel re yceived by the said secondary station and varying the frequency of the said unmodulated Wave until a beat frequency is obtained that lies within the range of frequencies adapted to pass through a band filter associated with the detecting circuit of the said secondary station.

4L. In a multiplex radio system comprising primary and secondary stations, the method of controlling the transmitting frequency of each secondary station, which consists in transmitting from the primary station a modulated Wave of fixed frequency, beating the received modulated Wave at the said secondary station with the unmodulated transmitted Wave of the said secondary station and adjusting the frequency of the said unmodulated transmitted Wave until the difference in frequency between the received modulated Wave and the unmodulated transmitted Wave Will be of such magnitude as to pass through a selective circuit associated with the receiving circuit of the said secondaryr station.

5. In a multiplexr radio system comprising primary and secondary stations, the method of controlling tl e transmitting frequency of a secondary station, which consists in transmitting from the primary station a w'ave of fixed frequency, beating the re ceived Wave at the said secondary station with the transmitted Wave of the said secondary station, and adjusting the frequency of the transmitted Wave until the beat frequency will .be of such magnitude as to pass throiiagh a selective circuit asso ciated Vwith the receiving circuit of the said secondary station.

6. ln a'multiplex radio system comprising primary and secondary stations, the method of controlling the transmitting frequency of a secondary station, which consists in transmitting from the primary station a Wave of fixed frequency, receiving the said Wave at the secondary station, generating at the secondary station a wave of different frequency and impressing the latter Wave upon the secondary rece fing circuit, together with the Wave received from said primary station, varying the frequencyof the Wave generated at said secondary station until the beat frequency of the tivo Waves lies Within the range of a selective circuit, and im.- pressing the resultant beat frequency upon detecting' apparatus.

7. ln a multiplex radio sistem, compris ing afplurality of primary and a plurality of secoinlary stations, each of the said primary stations having a transmitting chan nel, the method of controlling the transmitting frequency of a secondary station, which consists in transmitting over the said channel of each primary station a modulated wave of uxed frequency, which differs from that of other channels by a definitely fixed amount, assigning cach secondary station to its respective channel, generating a transmitting Wave at each secondary station, and beating the said transmitting` Wave with the Wave of the proper channel transmit-ted from the primary station to thel secondary station, varying the frequency of the said generated ware until a beat frequency is obtained that lies Within the range of frequencies adapted to pass through a band filter associated With the detecting circuit of the said secondary station.

S. ln a multiplex radio system compris ing a plurality of primary and a` plurality of secondary stations, each of the said primary stations having a. transmitting channel, the method of controlling the transmitting frequency of each secondary station, which consists in transmitting over the said channel of a primary station a Wave of fixed frequency which differs from that of other channels by a definitely fixed amount,.

assigning each secondary station to its respective channel, generating at each secondary station :i transmitting wave, dcmodulating the ware received from said primary station by the wave generated at said secondary station, varying the frequency of the generated wave until the resultant beat frequency is of such magnitude as to pass through a selective circuit associated with the detecting circuit of the receiving circuit. y

9. in radio system comprising primary and secondary transmitting channels, the method of controlling the transmitted frequency of secondary transmission channels, which consists in transmitting over a prichannela wave of assigned frequency, transmitting wave over a secondary channel, receiving both of said waves, causing them by interaction to produce a third frequency characteristic of the said two transmitted waves, and adjusting the frequency of the said secondary transmitted wave so that the said third frequency shall have an assigned value.

10. In a radio system comprising a. plurality of primary and a plurality of secondary stations, each of the said primary and secondary stations having one or more transmit-ting channels, the method of controlling the transmitting frequency of second.- ary stations which consists in assigning pairs, each composed of a primary transinittingr channel and a secondary transmitting channel forming a two-way communication channel, transmitting over a primary channel a modulated wave of fixed frequency, transmit-ting a wave over the corresponding secondary channel, beating the two waves together in the receiving apparatus of the secondary station and adjusting the frequency of the seconda-ry transmitting wave until the said beat frequency lies within the range of frequencies adapted to pass through a selective circuit associated with the secondary station.

il. in a radio system comprising a plurality of stations, the method of controlling from one station the transmitting` frequency of a second station, which consists in transmit-ting from the first stat-ion a modulated wave of fixed frequency, beating the received modulated Wave at the said second station with the unmodulated transmitted wave of the said second station and adjusting the frequency of the said unmodulated transmitted wave until the difference in frequency between t--e received modulated wave and the unmodulated transmitted wave will he of such magnitude as to pass through a selective circuit associated with the receiving` circuit of the said second station.

l2. in a radio system comprising a plurality of stations, the method of controlling` from the first station the transmitting frequency of a second station, which consistel in transmitting from the first station a modulated wave of fixed frequency, receiving the said modulated wave at the second station, generating at the second station an unmodulated transmitting wave and impressing a portion of the unmodulated wave upon the receiving circuit of the said second station together with the modulated received wave, varying the frequency of the unmodulated wave until the beat frequency of the two waves lies within t-he frequency range of a selective circuit, and impressing the beat frequency upon detecting apparatus 13. in a radio system comprising a plurality of stations, the method of controlling from one of said stations the transmitting frequency from aI second station, which consists in transmitting a modulated wave from the said first station, generating and transmitting an unmodulated wave from the said second station, impressing waves of both frequencies upon the receiving circuits at each station and varying the frequency of the wave generated and transmitted from the said second station until the beat frequency between t-he waves received at both stations will lie within a range that may be passed through the receiving circuit and detected. i

In testimony whereof, I have signed my name to this specification this 30th day of October, 1920.

RALPH BOWN. 

